On my 2018, in the last several days, with the true temp being from 25-35 degrees, the outside temp gauge would work for a while, then, erratically, it would drop to -30 or or more, then just go up and down constantly between 0 and -30 and then, sometimes up to normal, an even a couple of times, all the way to 70-80, before falling to -30 again.
Then, there are times it will blank out altogether. When it does this, the Auto-start/stop warning light comes on and the Service Engine Soon light comes on.
Here's the last crazy tidbit- when the outside temp is going up and down under 0 degrees, the inside heat barely heats, but as soon as the temp approaches the true temp OR (and this is crazy) the temperature goes out altogether, the heater kicks into normal mode.
My wife is scheduling an appointment. I know it happens, but having had the van for less than a month, it doesn't make us happy.